The present invention relates to a matrix incorporating medicaments for transdermal administration, particularly but not exclusively in the field of animal husbandry and to apparatus and techniques for administering veterinary medicaments transdermally.
Various techniques and devices are known for administering medicaments through the skin, particularly for veterinary use. One example of such a technique is described in U.S. Pat. No. 4,026,290, which suggests attachment of a device to the ears or tail of the animal for applying motion sickness mitigators, anti-migraine compounds, analgesics, anthelmintics, antiprotozoal compounds and systemic insecticides, miticide and acaricides.
Transdermal drug delivery in veterinary applications is discussed in an article entitled "Topical Drug Delivery to Cattle and Sheep" by Ian H. Pitman and Susan J. Rostas, in Journal of Pharmaceutical Sciences, Vol. 70, No. 11, November, 1981, pp. 1181-1193 and in an article by the same authors entitled "A Comparison of Frozen and Reconstituted Cattle and Human Skin as Barriers to Drug Penetration", in Journal of Pharmaceutical Sciences, Vol. 71, No. 4, April, 1982, pp 427-430. Transdermal drug delivery has been proposed for administering prophylactic medicaments in veterinary contexts but, to the best of the knowledge of the inventors, has not had any practical application of significance in veterinary practice.
Growth radiators and growth promoters, here collectively termed "growth promoters", are commonly used in veterinary applications and are often applied using implants which cannot be conveniently removed prior to slaughter. Hormones for synchronization in mammals are generally administered vaginally, a technique which requires skill and involves potential damage to the animal and could result in infertility.
In U.S. Pat. No. 4,638,043 (Szycher et al), there is disclosed a polyurethane matrix for dispensing drugs dispersed therein, primarily for incorporation in a medical patch comprised of successive layers of a substrate, a pressure sensitive adhesive, the drug dispensing matrix and optionally a second layer of adhesive. The matrix may also include (e.g.) polypropylene glycol, polyethylene glycol or glycerine, to soften layer softer and to aid the transport of the drug out of the matrix and into the skin.
As acknowledged in U.S. Pat. No. 4,767,402 (Kost et al), which discloses the use of ultrasound for enhancing transdermal drug delivery, relatively few drugs are known to be deliverable transdermally, insofar as the majority of drugs will not penetrate the skin at rates sufficiently high for therapeutic efficacy.
U.S. Pat. No. 4,792,450 (Kydonieus et al) discloses a transdermal drug delivery device which comprises a vinyl gel layer comprising PVC and a drug uniformly dispersed therein, the vinyl gel layer comprising a primary plasticizer for the PVC and an organic nonvolatile gel forming additive in an amount sufficient to form a gel. Examples of such additives are isopropyl palmirate, isopropyl myristate, soybean oil, castor oil, linseed oil, olive oil, mineral oil, petrolatum, caprylic/capric triglyceride and non-ionic surfactants.
In U.S. Pat. No. 4,818,540 (Chien et al), there is disclosed essentially a transdermal fertility-controlling polymer matrix dosage unit comprising an impervious backing layer, a polymer matrix disc layer adhered thereto containing microdispersed fertility-controlling estrogen and progestin hormones, and an adhesive layer for securing the dosage unit to the subject. The device may contain, preferably in the adhesive layer, but alternatively or additionally in the matrix layer, a skin permeation enhancing agent, in particular a fatty acid CH.sub.3 (CH.sub.2).sub.n COOH, where n is 2-16, isopropyl myristate or decyl methyl sulfoxide.
U.S. Pat. No. 4,820,525 (Leonard et al) discloses the use of a foamed polyethylene having specified properties, as a drug reservoir in a transdermal/transmucosal pharmaceutical delivery system. Thus, fertility hormones and albuterol were applied transdermally from such reservoirs attached to adhesive tape across nude mouse skin or cadaver skin, using menthol as penetration enhancer.
In U.S. Pat. No. 4,822,617 (Panoz), there is disclosed a device for the transdermal administration of skin-permable drugs (e.g. nitroglycerin, clonidin, methadone and scopolamine) in an ointment, cream or jelly-like carrier, comprising a laminar applicator adapted to receive a predetermined quantity of the drug on a skin-contacting surface thereof, the latter being overlaid by a drug-impervious layer to ensure a unidirectional transfer of the drug to the skin surface. In an exemplified embodiment, the applicator is loaded with a predetermined amount of ointment containing 2% nitroglycerin and lactose in an absorptive lanolin and white petrolatum base formulated to provide controlled release of the active ingredient. The entire contents of all of the foregoing U.S. patents are incorporated by reference herein.
It will be appreciated that adhesive patches, by means of which drugs are conventionally administered transdermally to humans, can result in skin irritation and sensitization with prolonged use. Shaving the hair from a suitable area may also be necessary. Adhesive patches would be quite unsuitable for animals, partly because of the great quantity of body hair in comparison with humans, and partly because adhesive patches would be liable to be rubbed off. By contrast, the present matrices can conveniently be used for transdermal administration to animals, by means of the devices described herein. Moreover, persons skilled in the art can readily appreciate that these matrices could also be readily adapted for human use, e.g. by securing to the arm or leg by a bandage which is impervious to the drug/carrier combination.
It may further be noted that the sense of the most of the prior art in relation to transdermal administration to humans is that only a restricted number of drugs are inherently suitable for this form of administration. It is believed that the present invention offers a means of transdermal delivery of a wider spectrum of drugs than has heretofore been made generally available, particularly to animals, but also to humans.
As indicated above, adhesive plasters incorporating medicaments for transdermal administration, which are known for application to humans, would be generally inappropriate for veterinary use.